Safe at Any Speed

Rotary instruments, better known as handpieces, are mainstays of modern dentistry. Handpieces used in dentistry are typically classified by their low-speed or high-speed motors, which are fitted with attachments such as angles and burs.

Low-speed handpieces do not operate higher than 40,000 rpm, though some models will reach up to 140,000 rpm. These tools, which feature latch-type chucks or friction-grip attachments, offer high torque to enhance power at low speeds. Speed and rotation can be adjusted through handle controls. Low-speed handpieces may be used in cavity preparation and for jobs such as caries removal, prophylaxis, prosthetic trimming, and implant and endodontic procedures. Thanks to their slow speeds, they do not generate high heat. This means low-speed handpieces don’t require cooling through water circulation.

High-speed rotary handpieces, on the other hand, are air-driven power tools. Operating from 100,000 to 400,000 rpm and higher, they are used for tasks such as cavity and crown preparation and in precision-type work such as polishing and shaping. They work by pushing air through the head, which causes the bur to spin. Due to their high speed, they require cooling via water and air to counteract overheating, which would not only damage the device, but injure the patient as well.

Both types of handpieces require regular maintenance. This in­cludes cleaning, lubrication, and sterilization between patients. When cleaning, most experts agree that handpieces should not be wiped down with chemical disinfectants, as this can lead to instrument corrosion. Instead, manufacturers will often recommend a germicidal de­tergent or handpiece cleaner and a small brush for external surfaces. Care must also be taken to clean components such as the chuck, grips and any recessed features. Some experts suggest that fiber optic or light-emitting diode lenses be cleaned with isopropyl alcohol, but that the use of sharp instruments should be avoided. Additionally, burs should never be left in place during the sterilization process.


POINT OF SALE | SPEED LIMIT

  • Both low-speed and high-speed handpieces are critical components of contemporary dentistry.
  • Handpieces require regular maintenance, and must be cleaned, lubricated and sterilized between patients.
  • The Centers for Disease Control and Prevention, as well as numerous dental organizations recommend or require the use of heat sterilization for all dental handpieces.
  • Autoclaves allow practitioners to safely satisfy sterilization requirements for handpieces and meet infection control standards.

Lubricants for low-speed handpieces are different from those formulated for high-speed handpieces. But in either case, after application into the drive air tube, the instrument should be run to expel excess liquid and ensure adequate lubrication. Sterilization is the final step in this process, which not only helps ensure longevity, but also goes a long way toward eliminating cross-contamination hazards.

In fact, with today’s very real concerns about infection control, sterilization protocols have never been so front and center. But while the dental profession has long had a handle on sterilization of hand instruments, actual sterilization of handpieces is a more recent protocol. It can also present challenges not inherent in the case of hand instruments, which can be immersed in an ultrasonic bath or placed in washer/disinfector units.


GUIDED RECOMMENDATIONS

rotary instruments

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Kathy Eklund, RDH, MHP, is director of Occupational Health and Safety at the Forsyth Institute in Cambridge, Massachusetts, as well an adjunct associate professor at the Massachusetts College of Pharmacy and Health Sciences, Forsyth School of Dental Hygiene, and current chair of Organization for Safety, Asepsis and Prevention. Eve Cuny, RDA, MS, is director of Environmental Health and Safety and an associate professor in the Department of Diagnostic Sciences at the University of the Pacific Arthur A. Dugoni School of Dentistry in San Francisco. Both are highly regarded infection control experts, who stress the wisdom in following recommendations set forth by the Centers for Disease Control and Prevention (CDC) to the letter.

According to the CDC, “Dental handpieces and associated attachments, including low-speed motors and reusable prophylaxis angles, should always be heat sterilized between patients and not high-level or surface disinfected. Although these devices are considered semicritical, studies have shown that their internal surfaces can become contaminated with patient materials during use. If these devices are not properly cleaned and heat sterilized, the next patient may be exposed to potentially infectious materials.”2

The CDC also provides a step-by-step protocol for cleaning and sterilizing handpieces that can be followed in addition to adhering to manufacturer recommendations.3

  1. Clean and heat-sterilize handpieces and other intraoral instruments that can be removed from the air and waterlines of dental units between patients.
  2. Follow the manufacturer’s instructions for cleaning, lubrication, and sterilization of handpieces and other intraoral instruments that can be removed from the air and waterlines of dental units.
  3. Do not surface-disinfect; use liquid chemical sterilants or ethylene oxide on handpieces and other intraoral instruments that can be removed from the air and waterlines of dental units.

WAKE-UP CALL

In the past, it was acceptable to merely wipe down a handpiece with a disinfectant, along with the occasional application of a lubricant. But studies using dye have shown that in high-speed handpieces, the dye is, indeed, retracted during use, only to be expelled intraorally in subsequent patients.1 To date, there have been no such studies on low-speed handpieces due to restricted physical access. Nonetheless, the potential for contamination potential is a reality for those systems, as well, and it is critical that they be adequately flushed for at least 20 to 30 seconds after each patient and proper barrier protection employed.1 More has also been learned in recent years about the longevity of pathogens. Research indicates that viral DNA and live viruses are retained in both high-speed and prophylaxis angles.1 The sum of all these findings is pretty unsettling, to say the least.

A couple of factors have come into play in regard to increased vigilance of handpiece sterilization practices. Due to an improved understanding of pathogens and the fact that they do not succumb to low-level disinfectants, coupled with the reality that more dentists are performining surgical procedures, including implants and bone grafts, it has become accepted practice in modern offices to clean and heat sterilize both low- and high-speed handpieces between patients. This is because handpieces, with all their tiny curvilinear crevices and working parts, can provide a safe harbor to pathogens lurking in tooth dust, saliva and blood. This heightens the importance of both a thorough scrubbing and sterilization of handpieces.

“We know that oral fluids may be retracted into air or waterlines of dental handpieces, so cross contamination via these devices is a real concern,” says Eve Cuny, RDA, MS, director of Environmental Health and Safety and an associate professor in the Department of Diagnostic Sciences at the University of the Pacific Arthur A. Dugoni School of Dentistry in San Francisco. “This leaves little question that best practice for protecting patients is to clean and sterilize handpieces according to the manufacturer’s instructions after every use.”

STEAM HEAT

The Centers for Disease Control and Prevention (CDC), the American Dental Association, and the Organization for Safety, Asepsis and Prevention (OSAP), as well as the majority of dental licensing boards and dental handpiece manufacturers agree that it is not enough to surface disinfect or immerse handpieces in chemical germicides, which may also result in corrosion. The recommendation is, instead, heat sterilization. These organizations stress that handpieces be heat sterilized between each patient after cleaning and lubrication.1,4-6

Kathy Eklund, RDH, MHP, director of Occupational Health and Safety at the Forsyth Institute in Cambridge, Massachusetts, as well an adjunct associate professor at the Massachusetts College of Pharmacy and Health Sciences, Forsyth School of Dental Hygiene, and current chair of OSAP, tells Mentor, “A number of states have adopted the CDC’s Guidelines for Infection Control in Dental Health-Care Settings—2003 as part of their dental licensing regulations. This can be verified on a state-specific basis by contacting the state dental board/dental licensing agency.” In fact, some states require heat sterilization of dental handpieces, including California, Florida, Indiana, Kansas, Missouri, New Mexico, Ohio, Oregon, South Carolina, Virginia, and Washington.

The upshot is that manufacturers are now engineering handpieces that can tolerate heat — up to 275-degrees Fahrenheit, to be exact. According to the CDC, the majority of today’s handpieces are now heat-tolerant to the point that they are autoclavable. Those that aren’t can reportedly be retrofitted to allow this method of sterilization.


LEXICON

Attachments: Can include straight attachments or nosecones and contra angle attachments.
Chuck: The part of the handpiece that holds the bur.
Contra angle: A handpiece attachment that’s angled to facilitate access to certain areas of the oral cavity.
Fiber-optic handpiece: Features a fiber-optic light to illuminate the oral cavity.
Nosecone: A straight attachment used on low-speed handpieces.
Semi-critical: A category of instruments based on infection transmission risk. Pertains to instruments that do not penetrate soft or hard tissues, but do contact mucous membranes or broken skin.


But Cuny notes that while manufacturers are designing handpieces and their attachments to be able to withstand the heat sterilization process, most handpieces cannot take the high temperatures involved in dry heat sterilization. For that reason, she says, “It’s usually necessary to have a steam autoclave available in the office.”

But while there is general agreement about the importance of heat sterilization, both Cuny and Eklund stress the gravity of adhering to manufacturer instructions for use, including reprocessing. Says Cuny, “It’s important to always check the manufacturer’s instructions for maintenance and sterilization because each handpiece has unique instructions. This means if the dental office has more than one type of handpiece, it may need separate cleaning and sterilization protocols for each.”

Eklund couldn’t agree more, adding, “The most important information sales reps can provide is to advise clients to follow the manufacturer’s directions. Each handpiece model has specific maintenance, cleaning and sterilization instructions. As is true with all products and devices, it is very important to follow the manufacturer instructions for use (IFU).”

Along these lines, Cuny says that when it comes to ensuring sterilization of handpieces, some of the challenges are related to inventory while others are related to time and available equipment. “Dental offices should ensure they have enough handpieces so they can sterilize each one in between every patient,” says Cuny. “It may be necessary to have an air station in the sterilization area to allow for circulation of a cleaner/lubricant before sterilization. Relying on this getting done in the dental treatment room can impact the amount of time it takes to make the room available for the next patient, reducing efficiency.”

HIGHS AND LOWS

Regardless of whether we’re talking about a low- or high-speed handpiece, Cuny says that because evidence indicates that the internal components of these devices can become contaminated during use, wiping the outside with a chemical disinfectant or covering with an impervious barrier is not enough to prevent cross contamination. For this reason, CDC guidelines specify that all handpieces and other devices that can be removed from the air and waterlines should be cleaned and heat sterilized between patients. Nonetheless, Cuny adds that there seems to be continued confusion over whether slow-speed motors require sterilization.

Indeed, Eklund reports that ever since the introduction of low-speed handpieces, the CDC has fielded numerous questions regarding the recommended sterilization of low-speed motors. She reports that the organization has attempted to clarify its recommendation in its 2016 summary of infection control document,2 which recommends that low-speed motors removed from air and waterlines be heat sterilized according to manufacturer instructions. “This is not a new recommendation, but reinforces the 2003 CDC recommendations.”

But it is a bit of a conundrum.


STEAM OF CONSCIOUSNESS

Steam autoclaves are, in essence, small pressure chambers that are designed to sterilize items — in this case, dental equipment such as handpieces through use of damp heat or steam. Temperatures can reach, but should not exceed 275-degrees Fahrenheit, and chemical and biological indicators are used to verify that the correct temperature has been reached to ensure sterility. Once the appropriate amount of time has passed for sterility, the autoclave will vent, releasing heat and pressure, and begin drying its contents.

Many of these devices are about the size of a microwave oven, and can be found on the countertops of dental practices and laboratories across the globe. They will typically offer trays onto which instruments contained in pouches can be placed. Today’s units are often engineered for push-button ease of operation, and some even expedite data management via digital transfer, and alert operators when water quality is subpar.


While Eklund notes that some of the newer low-speed cordless handpiece models are not connected to air/water lines of dental units and have sealed motors that prevent internal retraction of patient fluids, they are powered by a rechargeable lithium ion battery, and the motor cannot be sterilized. As Eklund explains it, “Each manufacturer of these low-speed handpieces has specific aseptic management IFUs that must be followed.”

According to Eklund, more emphasis is being placed on seamless designs, which facilitate cleaning. And a number of handpieces are now offered in lube-free iterations. Also, increasing numbers of motors are heat tolerant. In these cases, it is usually recommended that low-speed motors and attachments be placed in individual pouches for sterilization.

While handpiece innovations aimed at streamlining infection control are welcome news, Cuny notes, “Just the fact that most dental practitioners now sterilize handpieces between patients is a big positive change that has happened gradually since the 1980s.”

Disposable handpiece attachments have also become a reality. And perhaps the day will come when we will see single-use handpieces. But until then, by following the proper sterilization protocols, clinicians — along with their patients — can rest assured that the handpieces they use are safe at any speed.

 

REFERENCES

  1. Centers for Disease Control and Prevention. Recommended infection control practices for dentistry. MMWR Morbid Mortal Weekly Rep. 1993;42(RR-8):1–14.
  2. Centers for Disease Control and Prevention. Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care. Atlanta: Centers for Disease Control and Prevention, U.S. Department of Health and Human Services; October 2016.
  3. Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. 2003;52(RR-17):1–61.
  4. Student Doctor. The Dental Student Network list of state licensing agencies. Available at: studentdoctor.net/dental/state_boards.html. Accessed July 7, 2017.
  5. Council on Scientific Affairs and ADA Council on Dental Practices. Infection Control Recommendations for the Dental Office and Dental Laboratory. J Am Dent Assoc. 1996;127:672–680.
  6. Organization for Safety, Asepsis and Prevention. Infection Control for Dentistry Guidelines, September 1997.

 

Featured image by DMYTRO AKSONOV/E+/GETTY IMAGES PLUS

From MENTOR. September 2017;8(9): 16,18,20,22-23.

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